1. Field of the Invention
The present invention relates to a magnetic disk drive including a magnetic head for recording data onto a magnetic recording medium, such as a magnetic disk, and reading the data from the magnetic recording medium.
2. Description of the Prior Art
As shown in FIG. 10., a conventional magnetic disk drive includes a plurality (two being shown) of parallel spaced magnetic disks 1, 2 mounted on a single rotary shaft or spindle (not shown). An access arm 3 is driven by a voice coil motor (not shown) and movable in a direction parallel to the plane of the magnetic disks 1, 2. A pair of flexures 4, 5 each formed of a stamped plate spring are secured by clinching to opposite sides of the arm 3. The flexure 4 is disposed in confrontation with the magnetic disk 1, while the flexure 5 is disposed in confrontation with the magnetic disk 2. The flexures 4, 5 are bent inwardly toward each other at portions adjacent to the fixed ends thereof. Floating magnetic heads 6, 7 are carried on the distal ends of the respective flexures 4, 5 at the sides which face toward the corresponding magnetic disks 1. The magnetic heads 6, 7 have negative pressure or suction sliders 6a, 7a and, when the flexures 4, 5 are not subjected to external forces, the magnetic heads 6, 7 are spaced far from the recording surfaces of the respective magnetic disks 1, 2. The floating magnetic heads 6, 7 are identical in construction and hence a description given below is directed to only one magnetic head 6. The magnetic head 6 includes, as shown in FIG. 15, a pair of laterally spaced cores 6b, 6c attached to one side of the negative pressure slider 6a with a pair of spacers 6d, 6e of non-magnetic material disposed between corresponding ones of the cores 6b, 6c and the negative pressure slider 6a. The spacers 6d, 6e provide magnetic gaps between the negative pressure slider 6a and the magnetic cores 6b, 6c. The magnetic core 6b has a lead wire 6f wound therearound for performing magnetic data recording/reproducing operation through the lead wire 6f. The slider 6a is a substantially rectangular body of a magnetic material such as ferrite and includes a substantially U-shaped floating rail 6g which serves to develop a positive pressure as the magnetic head 6 approaches the magnetic disk 1 (FIG. 10). The U-shaped floating rail 6g has two recessed portions 6h, 6h at central portions of the respective arms and defines a rectangular central recess 6i which communicates with the recesses portions 6h. The central recess 6i serves to develop a negative pressure or suction when the magnetic head 6 approaches the magnetic disk 1. During that time, a stream of air flows from one side A (which is remote from the cores 6b, 6c) to the opposite side B of the magnetic head 6. Referring back to FIG. 10, a pusher rod 8 is disposed centrally between the flexures 4, 5 and is connected at its one end to a rotary shaft 8a. When the rotary shaft 8a turns about its own axis in the direction indicated by the arrow C in FIG. 10, the pusher rod 8 is displaced in a direction from the arm 3 toward the heads 6, 7, thereby forcing the flexures 4, 5 outwardly toward the magnetic disks 1, 2. For the purpose of forcing the flexures 4, 5, the pusher rod 8 is made of a rigid, inflexible material and has a diameter substantially the same as the width of the arm 3; if not so, the pusher rod 8, as it moves toward the heads 6, 7 to spread the flexures 4, 5, is flexed or bent at an intermediate portion thereof, thus failing to bring the flexures 4, 5 near to the magnetic disks 1, 2.
The conventional magnetic disk drive of the foregoing construction operates as follows.
The magnetic disks 1, 2 are rotated and, after a predetermined rotational speed of the magnetic disks 1, 2 is reached, the rotary shaft 8a is turned in the direction of the arrow C in FIG. 10 to thereby move the pusher rod 8 in the direction indicated by the arrow D shown in FIG. 11. Thus, the pusher rod 8 forces the flexures 4, 5 to resiliently deform or bend outwardly toward the corresponding magnetic disks 1, 2 so that the magnetic heads 6, 7 come close to the corresponding magnetic disks 1, 2, as shown in FIG. 12. When the magnetic heads 6, 7 reach the respective positions (floating positions) which are spaced from the magnetic disks 1, 2 by a predetermined distance, dynamic pressures are produced and act on the respective magnetic heads 6, 7 to hold them immovable while keeping a constant spacing between the magnetic heads 6, 7 and the magnetic disks 1, 2, as shown in FIG. 13. (This condition is referred to as "floating condition".) The magnetic heads 6, 7 while kept in the floating condition undertake the data recording/reproducing operation relative to the corresponding magnetic disks 1, 2. In this instance, each of the magnetic heads 6, 7 is subjected to a positive pressure tending to separate the magnetic head 6, 7 from the corresponding magnetic disk 1, 2, a negative pressure or suction tending to pull the magnetic head 6, 7 toward the magnetic disk 1, 2, and a resiliency of the corresponding flexure 4, 5 tending to pull the magnetic head 6, 7 away from the magnetic disk 1, 2. In the floating condition, a combined force of the positive pressure and the resiliency of the flexure 4, 5 is in balance with the negative pressure.
According to the conventional construction, the pusher rod 8 is likely to be displaced off the center between the two flexures 4, 5 due to an assembling error. If the pusher rod 8 is slightly displaced toward the magnetic disk 1 from the center between the flexures 4, 5, as shown in FIG. 14, the magnetic head 7 carried on the flexure 5 is far distant from the magnetic disk 2 beyond a predetermined spacing which is effective to produce the dynamic pressure acting on the magnetic head 7. The magnetic head 7 is, therefore, unable to float over the magnetic head 2 with the result that the data recording/reproducing operation cannot be performed. Furthermore, when the rotary shaft 8a is distorted, the pusher rod 8 moves at an angle to the plane of each magnetic disk 1, 2. In this instance, if the pusher rod 8 is displaced toward the magnetic disk 1 as shown in FIG. 14, the magnetic head 6 is forced into friction contact with the surface of the magnetic disk 1 and hence sustains damage or damages the magnetic disk 1.